Progress 07/01/90 to 06/30/91
Outputs
Our laboratory continues to provide research support for botulism of all species, but with emphasis on cattle and horses. We have investigated more than 50 outbreaks of botulism in cattle and horses in the past eight years and have isolated toxin and/or spores from specimens in 35 outbreaks. The CDC made available limited amounts of outdated trivalent (ABE) antitoxin for use in these outbreaks to treat affected animals. A pentavalent (ABCDE) antitoxin of equine origin has been developed for use in outbreaks. During the past year, our laboratory has developed an ELISA assay to measure antibody to Clostridium botulinum Type B. This technique will be used to critically evaluate vaccination protocols in horses and foals to determine the optimal time intervals to provide protection against Type B botulism. Data from this research is now being tabulated.
Impacts
(N/A)
Publications
- WICHTEL, J.J. and WHITLOCK, R.H. 1991. Botulism associated with feeding alfalfa hay to horses. J. Am. Vet. Med. Assoc. 199:471-472.
- CRANE, S.A., WHITLOCK, R. H., BUCKLEY, C. and FORNEY, B. 1991. Clostridium botulinum Type B toxoid for vaccination of adult horses, pregnant mares and foals: a study of vaccination protocols. Presented AAEP.
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Progress 01/01/90 to 12/30/90
Outputs
Our laboratory continues to investigate outbreaks of botulism in cattle, horses,dogs, cats and poultry. During this past year we investigated more than 60 occurances/outbreaks of botulism in animals. Clostridium botulinum isolations were attempted from submitted diagnostic specimens. Fecal specimens appear to yield the highest percentage recovery compared to food stuffs. Only rarely can the toxin be detected in the serum (most commonly in chickens and dogs). Our laboratory has developed an ELISA assay for Clostridium botoluinum type B antibody which compares favorably with the mouse bioassay. Several vaccination intervals (ranging from 1 wk to 4 wks) have been evaluated in adult horses. Animals vaccinated at one week intervals were found to develop a more rapid antibody response compared to horses vaccinated at one month intervals. However, to provide optimum protection the last dose of vaccine should be given one month after the 3rd immunization to develop the
highest titer.
Impacts
(N/A)
Publications
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Progress 01/01/89 to 12/30/89
Outputs
Our laboratory continues to provide research support for botulism of all species, but with emphasis on cattle and horses. We have investigated more than 40 outbreaks of botulism in cattle and horses in the past five years and have isolated toxin and/or spores from specimens in 30 outbreaks. The CDC made available limited amounts of outdated trivalent (ABE) antitoxin for use in these outbreaks to treat affected animals. Plans are underway to develop a pentavalent (ABCDE) antitoxin of equine origin which would serve as a repository depot of antitoxin for use in outbreaks. During the past year, our laboratory has begun the development of an ELISA assay to measure antibody to Clostridium botulinum Type B. This technique will be used to critically evaluate vaccination protocols in horses and foals to determine the optimal time intervals to provide protection against Type B botulism. Some funds were utilized to determine the extent of in-utero transmission of M.
paratuberculosis from infected dams to their fetus. Approximately 100 known infected cattle have been followed to slaughter to obtain fetal tissues, milk and supramammary lymphnode from the dam. Initial results suggest about 20% of the supramammary lymph nodes were positive on culture.
Impacts
(N/A)
Publications
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Progress 01/01/86 to 12/30/86
Outputs
The major effort this past year has been on Potomac Horse Fever. Our research has shown this disease not to be transmitted by contact but readily transmitted by blood transfusion. Recovered horses have a solid immunity. Attempts to identify a carrier among recovered horses and ponies has failed uniformly. However, recently, E. risticii was recovered from a pregnant pony mare that had been infected 6-7 months earlier. No organisms were able to be recovered from the mare's tissues. This would suggest that E. risticii may remain viable in the fetus of infected mares and be a potential source of infection to other animals. The plate latex agglutination test (PLAT) as distributed by ProtoTek was found to correlate fairly well with IFA but did give false positive and false negative results on occasion. A report is being prepared for publication. A preliminary trial with an experimental vaccine gave high antibodies in vaccinated ponies, which reached extremely high
levels following challenge with the line organism. However, the protection from developing clinical signs was incomplete.
Impacts
(N/A)
Publications
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Progress 01/01/85 to 12/30/85
Outputs
Our investigations have focused on Potomac Horse Fever, salmonellosis and Johne's disease. Potomac Horse Fever is not localized to Maryland as initially suspected, but now is recognized in more than 14 states including Canada. Epidemiologic studies confirm the seasonal nature (June to September) of the acute diarrheal disease which causes mortality in 20-30% of affected animals. Monoclonal antibodies have been produced against the causative agent Ehrlichia risticii which will be used to develop a more sensitive diagnostic test. Research to date indicates there is little risk of transmission from one infected animal with clinical signs to normal horses. The agent is present in the blood, but not in diarretic stool. Recovered horses are immune, but the duration of immunity is unknown. It is not known if recovered horses are carriers of the agent or not. Tetracycline appears to be effective when given after the development of clinical signs, but will not abort an
infection if given early in the disease process. Johne's disease was present in 7.2% of slaughtered cull dairy cattle in the northeastern U.S.A. The disease was not uniformly distributed among states nor within regions of Pennsylvania. The weight difference at slaughter was 129 lbs, or about $48.00/infected cow. Although the ages were similar between groups, the Johne's positive animals gave 3,216 lbs less the last lactation compared to the other cattle. The overall economic loss was estimated to exceed $5.
Impacts
(N/A)
Publications
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Progress 07/01/83 to 06/30/84
Outputs
During the past year our investigations have focused on the problem of acute diarrheal diseases in animals. A major new problem identified in horses was Potomac Horse Fever. This disease was first recognized as a clinical entity in Maryland farms along the Potomac River. It appears to be a seasonal disease (June to October) affecting all breeds, sexes and types of horses. Despite intensive therapy approximately 30% of the horses die. Our laboratory was the first to transmit the disease using whole blood and during the same time found to be a relatively non-contagious disease. Both incontact and horses challenged orally with fecal effluent did not contract the disease, suggesting a seasonal vector. Current opionins suggest the disease is transmitted by ticks. One research project evaluated tetracycline as a potential therapeutic agent. Tetracycline did delay the onset of cliical signs but did not prevent the disease even if administered prior to the horse
receiving the infected blood. The disease was able to be transmitted to mice but not to rabbits.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
A calf diarrhea model has been developed to evaluate a variety of agents as antidiarrheals. The model is reproducible and uses B-44 strains of E. coli. Lidamidine, zealites and antibiotics have been employed in this model system. A newly recognized (1979) diarrheal syndrome of horses - "Potomac Fever" has been further characterized as a seasonal infectious disease characterized by a high mortality - 30% despite intensive therapy. The agent is transmissable using whole blood to ponies and horses. The clinical signs consist of colic, anorexia, fever, depression and diarrhea. Leukopenia occurs in the majority of cases. Recovered horses are resistent to subsequent challenge.
Impacts
(N/A)
Publications
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